The invention relates to a process and a device for continuous reeling of a pulp sheet, particularly a paper sheet, e.g. tissue, where the sheet runs over a reel drum and is later wound on a winding unit.
Processes and devices of this kind have been known for some time in the production of paper sheet. The disadvantage of the devices known is that either the contact pressure of the horizontal reel on the reel drum is such that the horizontal reel is driven by the force generated by friction, as shown by U.S. Pat. No. 5,611,500 A (Smith) or U.S. Pat. No. 5,845,868 A (Klerelid et al.), or a separate drive is provided for the horizontal reel, as in DE 197 48 995 A1 (Voith), where the pressing force cannot be set exactly because there are too many points where non-calculable losses arise, e.g. due to friction. The pressure pre-set at the contact pressure cylinders thus does not define the actual pressing force between reel drum and horizontal reel. Low pressing force is desirable in particular for tissue with a high volume in order to avoid destroying the high volume again with the contact pressure. In the conventional devices known, however, the pressing force can only be set imprecisely and the losses due to friction in the mechanical parts already exceed the required contact pressure, thus it is impossible to control the pressing force exactly.
The aim of the invention is to propose a process and a device that are easy to control during the winding process, even at low contact pressures.
The invention is thus characterized by the pressing force in the nip between the horizontal reel (core shaft) and reel drum being measured without any losses. Since the measurement is taken without any losses, the contact pressure can always be determined exactly and adjusted continuously.
An advantageous further development of the invention is characterized by the reading measured for the pressing force being used to control the pressing force at a desired level. Thus, it is also possible to set a low pressing force.
An advantageous configuration of the invention is characterized by the pressing force and the regulating distance being controlled by a measuring system integrated into the pressure cylinders that generate the contact pressure.
A favorable further development of the invention is characterized by the pressing force at the reel drum being measured in the direction of the force. As a result, the influence of friction and any influence on the measurement reading by the unbalanced mass of the paper roll can be eliminated.
If the load-sensing device is pre-stressed, sustained contact is guaranteed between oscillating lever and load-sensing device.
If the pressing force is measured horizontally in an advantageous configuration of the invention, this guarantees that also any weight influences, which otherwise always have to be taken into account separately, are eliminated.
In a favorable further development of the invention, a pre-set pressing force in the nip is transferred via the paper roll to the reel drum by the hydraulic cylinders for the secondary arms, while the force applied by the hydraulic cylinders can be adapted continuously on the basis of the measurement readings from the load-sensing device and the pressing force in the nip can preferably be maintained at a constant level. As a result, it is possible to achieve a low pressing force and, in consequence thereof, maintain the volume, particularly with high-volume tissue paper.
The invention also refers to a device for implementing the process, with a reel drum and a horizontal reel, characterized by load-sensing devices being provided for measuring the nip force without losses. Since the measurement is taken without any losses, the contact pressure can always be determined exactly and continuously adjusted, even with low contact pressures.
A favorable further development of the invention is characterized by the horizontal reel being supported on load-sensing devices, preferably throughout the entire reeling process. As a result, it is possible to measure the contact pressure directly and without any losses, while guaranteeing uniform paper quality right through the entire reeling process.
An advantageous further development of the invention is characterized by the load-sensing devices being provided in a horizontally adjustable holding device. In this way, it is possible to guarantee a constant force direction and simple transfer of the (controlled) pressing force.
An advantageous configuration of the invention is characterized by the horizontally adjustable holding device being provided with support rollers that run in guide units, where the guide units are sealed off by a vertically arranged moving belt. This ensures safe and low-friction adjusting, which permits the contact force to be adapted precisely, even at low values.
A favorable further development of the invention is characterized by the endless belt being made of woven fabric, synthetic material or steel. In this way, the most favorable solution can be sought in each case depending on the requirements and environment.
An advantageous further development of the invention is characterized by the vertically arranged moving belt being a continuous loop running round two rolls provided at the ends of the guide units. This arrangement provides a frictionless seal.
A favorable configuration of the invention is characterized by the deflection rolls having trapezoidal grooves to guide the belt, with the endless-woven belt at least having a trapezoidal profile that meshes into the trapezoidal grooves in the deflection rolls. This permits very good lateral belt guiding, where there can be no friction losses and the belt cannot run off track to the side.
A favorable further development of the invention is characterized by the reel drum being supported on vertical oscillating levers and a load-sensing device being inserted between the oscillating levers and a fixed counterpart. In this way, the influence of friction and any influence on the measurement reading by the unbalanced mass of the paper roll can be eliminated.
If the oscillating levers have tensioning elements that press these levers against the load-sensing device, sustained contact can be guaranteed between oscillating lever and load-sensing device. This also guarantees a continuous signal for a control device.
Here the tensioning elements can be mechanical with, for example, springs, or hydraulic or pneumatic with, for example, cylinders.
If the load-sensing device is mounted firmly in horizontal direction in the horizontal plane of the reel drum axis, this guarantees that also any weight influences, which otherwise always have to be taken into account separately, are eliminated.
With all of these measures, it is possible to guarantee exact measurements and maintain the contact pressure at a constant level at virtually any stage of the reeling process.
By inserting the load-sensing device at the fixed reel drum, exact measuring is always guaranteed, even if a roll (horizontal reel) is changed. This precision is not ensured in other known systems due to the time factor pressure during roll change, which often results in inexact work, and due to the resulting additional, non-calculable friction influence.